A Monocular Structured Light-Based System for 3-D Reconstruction and Defect Detection of Municipal Pipeline Inner Walls

Municipal underground pipelines are closely intertwined with the daily lives of citizens. However, as a result of manufacturing imperfections and prolonged usage, pipelines frequently develop defects such as bulges, cracks, and damage. These issues can lead to leaks or complete failures, resulting in significant inconvenience for the public and substantial economic losses. Therefore, regular inspection and quality assessment of the inner walls of pipelines are essential. This article presents a monocular structured light-based system for the 3-D reconstruction of pipeline inner walls. The proposed system uses a laser emission unit and an industrial camera acquisition unit to generate a 3-D point cloud of the pipeline’s inner surface, enabling the quantitative detection of defects. The system only requires a single calibration and can achieve a 360° unobstructed reconstruction of the entire inner wall. The camera is triggered by an encoder to produce real-time point cloud data. The system underwent testing on pipelines without defects, pipelines with quantified defects, and pipelines with irregular defects. The experimental results demonstrate that the generated point clouds can effectively quantify defects and assess the quality of the pipeline’s inner walls with millimeter-level accuracy.